After run, Peg cuts slim figure (8)
I believe the answer is:
thirteen
'figure' is the definition.
'after run peg cuts slim' is the wordplay.
'after run' becomes 'r' (cricket abbreviation. I am not sure about the 'after' bit.**).
'peg' becomes 'tee' (tee is a kind of peg).
'cuts' means one lot of letters goes inside another (some letters cut their way into other letters).
'slim' becomes 'thin' ('thin' can be a synonym of 'slim').
'r'+'tee'='rtee'
'rtee' put within 'thin' is 'THIRTEEN'.
(Other definitions for thirteen that I've seen before include "ill-omened figure" , "Half of what's left [26D]" , "Cardinal" , "this could be unlucky" , "Supper attendees" .)